Hot gas engine with gas pressure control means



P 16, 1969 R. H. BRANDES 3,466,867 v HOT GAS ENGINE WITH GAS PRESSURECONTROL MEANS Filed Dec. 13, 1967 HEATER STORAGE TAN K GAS 5:1 OMPRESSORINVENTOR.

BY (30; A. Bram/es AT TOR N EY United States Patent O 3,466,867 HOT GASENGINE WITH GAS PRESSURE CONTROL MEANS Roy H. Brandes, Utica, Michassignor to General Motors Corporation, Detroit, Mich, a corporation ofDelaware Filed Dec. 13, 1967, Ser. No. 690,144 Int. Cl. F02g 1/04, 3/02US. Cl. 60-24 11 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THEINVENTION This invention relates generally to external combustion hotgas engines and more specifically to means for controlling the gaspressure in such an engine.

It is known in the art relating to closed cycle hot gas enginesoperating, for example, on the Stirling cycle, to control the poweroutput of such engines by varying the quantity of gas in the engineworking space. It is also known, for efficiency purposes, to use as aworking gas, a light gas such as hydrogen, and to provide pressurecontrol means including a storage tank from which gas is supplied to theengine working space and to which gas is returned when it is exhaustedfrom the engine working space. A compressor is used to return the gasfrom the engine working space to the storage tank.

One such gas pressure control arrangement is shown in United Statespatent application Ser. No. 522,553, Brandes. This arrangement, whilebeing an improvement over certain prior arrangements, is similar to someof them in that its utilizes a single fill valve connecting the storagetank to both the engine working and butter spaces in combination with apair of check valves which are used to prevent undesired bypassing ofgas between the spaces.

While such an arrangement may operate satisfactorily, it has been foundin practice that the pressure fluctuations in the working and bufferspaces have a deleterious efiect on the durability of the check valvesso that they may begin to leak. This results in undesired bypassing ofthe working gas and a loss of engine efiiciency.

An additional characteristic of the above noted system is that thestorage tank can never be exhausted below the lowest cyclic pressurefound in the engine working and buffer spaces. As a result, it is notpossible to use all the gas contained in a storage tank before it mustbe refilled or replaced.

SUMMARY OF THE INVENTION The invention also provides for a supply tankseparate from the storage tank and means to transfer gas from the3,456,867 Patented Sept. 16, 1969 "Ice supply tank to the storage tankso as to maintain the storage tank pressure above the desired minimum.The arrangement provides that this transfer is made by admitting gasfrom the supply tank to the inlet of the storage tank gas compressor sothat the supply tank may be completely exhausted before it is replacedby a full tank of gas.

These and other advantages of the invention will be more readilyapparent from the following description of a preferred embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 of the drawings illustrates ahot gas engine having gas pressure control means according to thepresent invention;

FIGURE 2 shows a portion of the gas pressure control means of FIGURE 1showing the actuating means in position to exhaust gas from the engineworking and buffer spaces for return to the storage tank; and

FIGURE 3 shows a portion of the gas pressure control means of FIGURE 1showing the actuating means in position to transfer gas from the storagetank to the engine working and buffer spaces.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more specifically tothe drawing, numeral 10 generally indicates a hot gas engine having acylinder 12 which is enclosed at its upper and lower ends. A powerpiston 14 and a displacer piston 16 are coaxially arranged toreciprocate in the cylinder in out of phase relationship as determinedby the connection of coaxial connecting rods 18 and 20 with suitablemechanism (not shown). Power piston 14 divides the space within cylinder12 into a working space 22 above the power piston and a buffer space 24below the power piston. The displacer piston reciprocates completelyWithin the working space and separates it into two portions which areinterconnected externally of the cylinder through a cooler 26, one ormore regenerators 28 and a heater 30 all of which comprise portions ofthe working space and arranged in a conventional manner.

In the operation of the engine, working gas, such as hydrogen, isretained within the working space under a substantial pressure. Theaction of the power and displacer pistons provide for a cycle ofoperation in the working gas including compression, heating, expansionand cooling phases which result in a net work output to the powerpiston. In order to reduce mechanical loads on the operating mechanism,the buffer space 24 is also filled with compressed gas approximatelyequal to the working pressure but which varies in pressure in a cycleopposite to that of the gas in the working space.

In order to change the power output of the engine, means are providedfor varying the quantity of gas in the working space by supplying gasthereto or exhausting gas therefrom. Since this variation changes theaverage working pressure level in the working space, the control meansare arranged to transfer gas to and from the working and buffer spacesat the same time. In this way the desired relationship between thepressures in the two spaces is maintained.

As shown in the figure, the control system comprises a supporting member32 which carries a working space fill valve 34, a buffer space fillvalve 36, a buffer dump and bypass 38 and a dump valve 40. All thevalves are illustrated as being spring biased ball elements actuated byrod-like actuators 42 although it should be understood that any suitablevalve construction could be used. An actuating lever 44 pivotallymounted on support 32 engages the valve actuators 42 and is movable bythe upward bias of a spring 46 opposed by a fluid actuated piston 48reciprocably carried in a cylinder 50.

Fill valve 34 connects through a fill line 52 with the engine workingspace 22 while fill valve 36 connects through fill line 54 with theengine bulfer space 24. Both valves are joined by a line 56 and aresupplied with gas through a line 58 connecting them with a fill limitingvalve 60.

Valve 60 is illustrated as including a spring biased ball element 62operable by a pressure actuated piston member 64. Of course, as in thecase of the fill valves, any other suitable valve construction could beused. Valve 60 is arranged when open to connect line 58 with a supplyline 66 leading from a Working gas supply tank 68. Tank 68 is connectedto a gas compressor 70 through a line 72 and the gas compressor is, inturn, connected through lines 74 and 76 with a supply valve 78. Thesupply valve could be of any suitable type, but it is illustrated asbeing constructed similarly to the fill limiting valve 60 in that itcontains a spring biased ball element 62 operable by a pressure actuatedpiston 64. When open, supply valve 78 connects line 76 with a supplytank 80 through a supply line 82. Coupling means 83 in the line providesfor replacement of an empty supply tank with a full one. A pressure line84 is also provided to connect the pressure in storage tank 68 to oneside of the piston 64 of supply valve 78.

Lines 74 and 76 also connect the gas compressor with dump valve 40. Theother side of this valve connects through lines 84 and 86 to the engineworking space 22. Line 84 also connects with dump and bypass valve 38,the other side of which connects through line 88 with the engine bufferspace 24.

Engine working pressure is transmitted to one side of piston 64 of thefill limiting valve 60 through a line 90 connecting the limiter valve 60with the working pressure side of dump valve 40.

The operation of the above described system is as follows. When theengine working space contains the proper quantity of gas to maintain theworking pressure at that for which the control is set, the systemremains in a neutral position as shown in FIGURE 1 wherein all the fill,dump and bypass valves are closed.

If, however, it is desired to reduce the working pressure, and alongwith it the buffer pressure, a control m mber (not shown) increases thefluid pressure on piston 48 causing lever 44 to be pivoted downwardly asshown in FIGURE 2. This action opens valves 38 and 40, cansing theworking and buffer spaces to be connected through valve 38 and lines 86,84 and 88 and permitting gas to fiow therefrom through valve 40 andlines 76 and 74 to the gas compressor 70. This gas is then pumpedthrough line 72 to the working storage tank 68 until a sufiicientreduction in the working and buffer spaces is obtained at which time thecontrol mechanism is returned to the neutral position of FIGURE 1 byaction of the external control means (not shown). During the time thepressure reduction is taking place, engine power is reduced by thebypassing of gas through valve 38 between the working and butter spacesof the engine.

If now an increase in the engine working and buffer gas pressures isdesired, the pressure acting on piston 48 is reduced, permitting lever44 to pivot upwardly and open the fill valves 34 and 36 as shown inFIGURE 3. Assuming fill limiting valve 60 is open, this permits gas toflow from storage tank 68, through line 66, valve 60 and line 58 to fillvalve 36. From this point, some of the gas passes through the valve 36and line 54 to the butter space 24 and the rest passes through line 56,valve 34 and line 52 to the working space 22. When the pressure in theworking and butter spaces reaches the desired value, the mechanism isagain returned to the neutral position of FIGURE 1.

Should the pressure in the working space increase to a predeterminedlimit, the working pressure will be transmitted through line 90 to thepiston 64 of the fill limiting valve 60, closing the valve andpreventing the admission of further gas to the working and buffer spaceseven though the control means has not yet returned to the neutralposition.

In order for satisfactory operation of the above described portion ofthe system, the pressure in the working storage tank 68 must always bekept at a higher level than the highest pressure reached in either theworking or buffer spaces of the engine. If this were not the case,undesired bypassing of gas between the working and buffer spaces couldoccur when the engine is being filled due to the connection of thesespaces through the fill valves 34 and 36. In order to avoid this, thepressure in the working storage tank 68 is transmitted through line 84to one side of piston 64 of the supply valve 78. When the storage tankpressure drops to a predetermined minimum, the piston moves rightwardly,Opening the valve and permitting gas from supply tank to pass throughlines 82, 76 and 74 to the inlet of the gas compressor by which it ispumped into the storage tank. Gas flow from the supply tank continuesuntil the pressure in the storage tank rises sufiiciently to again closethe supply valve 78. By this means, the replacement of gas leaking fromthe engine during operation is provided for. Since the supply tankdischarges to the inlet side of the gas compressor, the complete supplyof gas in the tank may be exhausted before the tank must be recharged orreplaced by a full tank.

It should now be apparent that the gas pressure control means formingthe present invention provides a system which operates without the needfor check valves in the lines connecting with the engine working andbuffer spaces and accordingly avoids the problems which have occurredthrough the use of these valves. While various specific valve andcontrol mechanisms have been illustrated to aid in the description ofthe invention, it is not intended that these structures should limit theinvention in any way. It is obvious that any suitable valves ormechanisms having the same functions could equally well be used whereappropriate.

While the invention has been described by reference to a singleembodiment, it should be apparent that numerous changes could be madewithout departing from the spirit and scope of the invention which isaccordingly to be limited only by the language of the following claims.

I claim:

1. In combination with a hot gas engine having a plurality of gascontaining enclosed spaces arranged to cyclically vary in pressure inout of phase relation to one another, gas storage means, meansconnecting said enclosed spaces with said gas storage means fortransferring gas therebetween and control means associated with saidconnecting means to control the gas pressure in said spaces, saidcontrol means comprising a plurality of fill valves in said connectingmeans, one

intermediate each of said enclosed spaces and said gas storage means andoperable to permit the transfer of gas to said spaces, actuating meansadapted to contact said fill valves and operable to open all said valvesconcurrently, and

means to maintain said gas storage means at a minimum pressure greaterthan the maximum pressures of said enclosed spaces,

whereby flow through said fill valves is unidirectional and bypassing ofgas between said enclosed spaces through said fill valves is prevented.

2. In combination with a hot gas engine having a cylinder, a powerpiston in said cylinder and, in part, defining at opposite ends of saidpiston a pair of enclosed variable volume gas containing spaces, gasstorage means, means connecting said enclosed spaces with one anotherand with said gas storage means for transferring gas therebetween andcontrol means associated with said connecting means to control gastransfer therethrough, said control means comprising a pair of fillvalves, one intermediate each of said enclosed spaces and said gasstorage means and operable to permit the transfer of gas to said spaces,actuating means adapted to contact said fill valves and operable to openboth said valves concurrently, and means to maintain said gas storagemeans at a minimum pressure greater than the maximum pressures of saidenclosed spaces,

whereby flow through said fill valves is unidirectional and bypassing ofgas between said enclosed spaces through said fill valves is prevented.

3. The combination of claim 2 wherein said enclosed spaces include aworking space wherein said gas goes through a heat power cycle by whichheat energy input is converted to work output to the power piston, and

a bufier space wherein pressurized gas, at least in part, balancesworking gas pressures on the engine power piston.

4. In combination with a hot gas engine having a working space and abuifer space, gas pressure control means comprising gas storage meansmeans including a compressor to maintain said gas storage means at aminimum pressure greater than the maximum pressures of said working andbuffer spaces,

a first fill valve connecting with said storage means and with saidworking space to control the supply of gas to said working space,

a second fill valve connecting with said storage means and with saidbuffer space to control the supply of gas to said bufier space,

a bypass valve connecting with said working and buffer spaces to controlthe bypassing of gas therebetween,

a dump valve connecting to one of said working and bulier spaces and tosaid compressor to control the discharge of gas from said working andbuffer spaces, said compressor being operable to receive gas from saiddump valve and to deliver said gas to said gas storage means, and

means for selectively operating said valves to vary the quantity of gasin the Working and buffer spaces of the engine.

5. The combination of claim 4 wherein the valve operating means ismovable to a plurality of positions including a first position whereinsaid fill valves are open to supply gas to the working and bufi-erspaces,

a second position wherein all said valves are closed to hold constantthe quantity of gas in the working and buffer spaces, and

a third position wherein said bypass and dump valves are open to exhaustgas from the working and buffer spaces and to bypass gas between saidspaces to reduce engine power.

6. The combination of claim 5 wherein said gas storage pressuremaintaining means further includes a gas supply tank,

means connecting said supply tank with said compressor to supply gastherethrough to said gas storage means, and

a supply valve in said connecting means and operatively connected withsaid gas storage means to control the supply of gas from said supplytank so as to permit gas flow to the compressor whenever the gaspressure in said storage means reaches a predetermined minimum.

7. In combination with a hot gas engine having a working space and abuffer space, gas pressure control means comprising a gas supply tank,

a working gas storage tank,

means connecting said supply tank with said storage tank and including acompressor operable to receive gas from said supply tank and to delivergas to said storage tank and means controlling the delivery of gas fromsaid supply to said compressor to maintain a minimum gas pressure insaid storage tank greater than the highest pressure existing in saidworking and buffer spaces,

a first fill valve conecting with said storage tank and with saidworking space and controlling the supply of gas to said working space,

a second fill valve connecting with said storage tank and with saidbuffer space and controlling the supply of gas to said buffer space,

a bypass valve connecting with said working and buffer spaces andcontrolling the bypassing of gas therebetween,

a dump valve connecting to one of said working and bufier spaces and tosaid compressor, said compressor being operable to receive gas from saiddump valve and to deliver said gas to said storage tank, and

means for selectively operating the valves to vary the quantity of gasin the working and buffer spaces of the engine.

8. The combination of claim 7 wherein said valve operating means ismovable to a plurality of positions including a first position whereinsaid fill valves are open to supply gas to the working and buffer spacesa second position wherein all said valves are closed to hold constantthe quantity of gas in the working and buffer spaces, and

a third position wherein said bypass and dump valves are open to exhaustgas from the working and buffer spaces and to bypass gas between saidspaces to reduce engine power.

9. The combination of claim 8 wherein said means controlling thedelivery of gas from said supply tank to said compressor comprise asupply valve connected between said supply tank and said compressor, and

a pressure responsive actuator connected with said storage tank andresponsive to a reduction in pressure therein to a predetermined minimumto open said supply valve and permit the passage of gas from the supplytank, through the compressor to the storage tank.

10. The combination of claim 8 wherein said dump valve connects withsaid working space and further comprising a pressure responsive valveconnected between said storage tank and said first and second fillvalves and operable to cut ofi the supply of gas to said fill valves,said limit valve being connected with the engine working space andoperable in response to the existence of a predetermined maximumpressure therein to cut off said gas supply.

11. The combination of claim 10 wherein valve operating means include apressure responsive actuator operable in response to a pressure signalto move said operating means to a selected one of said plurality ofpositions.

References Cited UNITED STATES PATENTS 2,746,241 5/ 1956 Dros 60-242,794,315 6/1957 Meijer 6024 2,966,034 12/ 1960 Gifiord 62--6 3,036,4275/1962 Meijer 62-6 3,355,881 12/1967 Brandes 6024 3,397,533 8/1968Steiner 6024 WILLIAM J. WYE, Primary Examiner.

US. Cl. X.R.

